Magnetic device



March 10. 193.1. E. J. PRATT MAGNETIC DEVICE Filed March 26, 1930 3Sheets-Sheet l //W/vr0/? EJPRATT BY 01am 6.7M

ATTORNEY March 10, 1931. J. PRATT 1,795,439

MAGNETIC DEVICE Filed March 26. 1930 3 Sheets-Sheet 2 INVENTOR E.J.Pe4rr5y Wm M ATTORNEY March 10, 1931. E. J. PRATT 1,795,439

' MAGNETIC .DEVIGE Filed March 26, 1930 3 Sheets-Sheet 3 INVE/VTUA E. J.F'knrr Arm/WE) Patented Mar. 10, 1931 UNETEI) STATES PATENT OFFICE RIES,INCORPORATED,

EDWAI'LD J. PRATT, OF NEN YORK, N. Y., ASSIGNOR TO BELL TELEPHONELABORATO- OF NEW YORK, N. Y., A CORPORATIQN OF NEW YORK MAGNETIC DEVICEApplication filed March 26, 1930.

lhis invention relates to magnetic devices and particularly to suchdevices when em played in meters, relays, ringers, loud speakers and thelike.

One object of this invention is to increase tine sensitivity, to improvethe efficiency and to in are greater reliability of operation ofmagnetic devices.

One feature of this invention resides in so constru ing a magneticdevice that there a relatively greater freedom of movement of itsmovable element as well as the see of greater liuX densities in the airbetween the movable and fixed elements the magnetic device withoutinterfering th its e'lfciency or inviting undesirable of the movableelement.

Another feature of this invention consists l e movable member employedin the magdevice, said member being so shaped produce a slight amount ofmagnetic when it is in either of its extreme posicordance with thisinvention there is d a magnetic device embodying the of this inventioncomprising a permagnet having pole'pieces attached its extremities, saidpole pieces having to restricted portions in which energizing coils areonnd, and armature comprising parallel pieces disposed one above and onebelow said coils and arranged to oscillate in such a manner to overlapthe restricted portio: s of said pole pieces and the unrestrictedportions on either side of the restrictions.

Amore complete understanding of this 111- vention will be obtained byreference to the appended drawings wherein:

1 is a front elevation of the magnetic device comprising this inventionemployed in telephone register;

Fig. 2 is a plan view of the magnetic device of 1 sliowing its structuremore in detail;

Serial No. 438,976.

Fig. 4 shows the armature of the magnetic device in one of its operablepositions;

Fig. 5 shows the magnetic device of Figs. 1 to 3 as amagnet motor in aringer; and

Figs. 6, 7 and 8 illustrate the application of this invention to arelay.

The magnetic device comprising this invention is shown in Figs. 1, 2 and3 applied to a device for registering the time of duration of telephonecalls. Mounted on a base plate 1 and spaced therefrom by a member 5, forinstance of brass, is a U-shaped permanent magnet 4:. Fastening screws 6hold the magnet and spacing member in the desired position on and withreference to the base plate. The magnet 4 is provided with pole pieces15 preferably built up of a plurality of laminations 27 which may be ofsoft iron, or, as found satisfactory in a model embodying the featuresof this invention, of a nickel-iron alloy comprising approximately 05%iron and 45% nickel. It has been found desirable to form one laminationof each of said pole pieces with spaced projecting portions 12 betweenwhich the polar eX- tremities of the permanent magnet are thrust andheld therein by drawing portions 12 together by means of bolts 14 andnuts 13. P0- sitioned between the innermost laminations of each polepiece is a member 7, of non-magnetic material, such as brass, which isprovided with forwardly extending arms 8 and with projecting portions 29through which latter projects one of the screws 16 which secure togetherthe laminations 27 of the pole pieces 15. Each pole piece has arestricted portion intermediate its ends in which a coil 19 is wound.The coil winding terminations 39 are connected to wires in the cords 17whose other ends are secured to the binding posts 3 1, 35, 36 and 37 onthe terminal block 88. To the proper terminals, for instance as shown,may be connected the telephone line 3 is an end view of Fig. 2 alongline wires and the telephone wires leading to the subscribers subset. Anarmature comprising parallel pieces 18, secured by the screws 30 to aspacer member 31 of non-magnetic material and held at a desiredseparation thereby, is pivotally supported on the pivot points 40 ofscrews 9 which thread through the forwardly extending arms 8 of themember 7. W hen the armature has been properly positioned by adjustmentof set screws 9, the latter may be held in their adjusted positions bylock nuts 10. It will be noted that each armature piece has enlargedextremities 118 the purpose of which will be more fully explained withreference to Fig. l. The armature pieces are adapted for movement inplanes parallel to those of the lateral faces of the pole pieces 15 andfor oscillation on the pivot points ll) so that they overlap both therestricted and non-restricted portions of said pole pieces. The movementof the armature in response to the periodic reversals in the directionof current flow through the coils 19 may be communicated to a suitablegear train by means of the pawls' 20 and 28 engaging with the ratchet 21and secured to the spacer member 31 by screws 33. Secured to the shaft23 with the ratchet 21 is a spur gear 22 which meshes with a second gear24: mounted on a shaft 25 carrying at one end thereof a pointer 26capable of indicating on av dial (not shown), for visual inspection, thetime of duration of a particular call, or for indicating thecumulative'time duringwhich use was made of a particular subscribersline over a given period. It is to be understood that th gear trainshown is merely illustrative and might be similar to that shown in thepending application of E. J. Pratt and D. D. Miller, filed May 31, 1929,Serial No. 367,490. The degree of movement of the armature may belimited by screws 11 which thread through the member C, may be screwedin or out to a desired extent and then secured in the usted position bytightening the lock nuts 41 against the member 7. The magnetic devicemounted on the base plate 1 may be enclosed in the protector casing 2which is secured to the base plate by means of screws 3.

The armature has been described as comprising two spaced parallelmagnetic pieces 18 pivotally supported for oscillation in planesparallel to the lateral faces of the pole pieces 15. As shown by Fig. 2,each armature piece.

has enlarged extremities which are so shaped that when the armaturepiece is in the position shown, each extremity overlaps the restrictedand nonrestricted portions of the pole piece face adj acent thereto. VJhen the armature is centered, say along the line B-B in its extremeright hand position, portions of the periphery of each armature piecewill be sub stantially in alignment with one edge of the restriction ineach pole piece and each extremity of the armature will overlap both therestricted and non-restricted portions of the pole piece. This is shownclearly in Fig. 4 the armatures position being indicated by the dottedlines. V fhen the armature piece is in its extreme left hand positioncentered along the line CG, portions of the periphery of said armaturepiece will likewise be substan tially in alignment with one edge of therestriction in each pole piece. The portions of said armature piece sosituated are the lateral edges of the extremities thereof. When thearmature is in either of the extreme positions represented by the centerlines B-B and CC, it will be held thereat by a slight biasing forceresulting from the armatures peculiar shaping. Nhen the armature is inother than its extreme positions this biasing force does not exist. Thiscondition can be 0btained, it has been found, by properly proportioningthe width of the armature to that of the coil restriction.

inasmuch as the armature comprises two pieces which are rigidly securedtogether, the position assumed by one armature piece will likewise beassumed by the other. The oper ation of this device, therefore, will beexplained with reference to the reactions of one armature piece only, itbeing understood that that of the other armature piece will be similar.Refer now to Figs. 2 and l. The telephone register may be located eitherat the central ollice or at the subscriber substation and the energizingcoils 19 are connected in series with the telephone lines leading tosaid substation. The initial position of the armature is immaterialsince the device is to measure successive units of conversation timewhich are measured by the periodic reversals of the talking current inthe telephone lines over which a talking circuit has been completed.Assume that the armature is in the position illustrated by Fig. 2 orcentered along the line AA of Fig. a an 1 that there is no talk ingcurrent flowing through the energizing coils 19. The main polarizingflux of the permanent magnet polarized as indicated, will have thefollowing circuit: N, non-restricted portion 42 of one pole piece,armature 13, non-restricted portion 15 of the other pole piece, to S ofthe permanent magnet. Another circuit will be: N, nonrestricted portion42 of one pole piece, armature 18, nonrestricted portion 14. of theother pole piece, to S of the permanent magnet. The main polarizing fluxwill also have similar paths through the other armature piecedisposechadjacent the other and lower lateral faces of the pole pieces.Assume now that a talking circuit has been completed through the telephone lines with which the coils 19 are in series. If the current flowis in one direction the polarizing ma netic flux will be strengthened inregions 23 and d4 of the pole pieces and weakened in regions l2 and 15and, to maintain the reluctance of the magnetic cirl an the lateral cuitat a minimum, the armature piece will oscillate on its pivot points tocenter along the line BB in one extreme position. WVhen at thetermination of a definite interval, the direction of flow of the talkingcurrent is re versed, the magnetic flux in regions 42 and 45 will bestrengthened and that in regions 43 and 44: weakened, whereby thearmature piece, in again endeavoring to assume a position in which thereluctance of the magnetic circuit is at a minimum, oscillates to aposition centering along the line C-C. It will be noted that theportions 42, a and 43, dlof the pole pieces are diagonally opposite ornoncontraposed and are in a similar magnetic condition at the same time.If the subscriber, against whom the units of conversation time are beingcharged, continues to use the circuit, the oscillations of the armaturepiece likewise continue as long as the periodic reversals of thedirection of flow of the talking current take place. The other armaturepiece, it is understood, will react likewise. Each oscillation of thearmature is communicated to the gear train by means of the pawls and 28,whereby the time of use of the telephone lines may be recorded. It is tobe understood that the armature pieces and spacer are made sufficientlyheavy so that the armature will not respond to momentary impulses, eventhough they greatly exceed the normal actuating forces.

It will be apparent from Fig. 3 that the armature pieces 18 are veryclosely adjacent faces of the pole pieces 15 and that the air gapsbetween said faces and said armature pieces, are very small. This ispossib e inasmuch as the armature pieces are, by this invention, adaptedfor movements in planes parallel to those of the faces of the polepieces and, though the air gaps be small, are in no danger of freezingthereto. These small air gaps permit of the use of high iiux densitiesand result in a much more efficient magnetic device.

In Fig. 5, the magnetic device described with reference to Figs. 1 to 4is employed as a magnet motor in a polarized ringer. A reed 4-7 isscrewed into the spacer member 52 and is provided with a weighted end 48positioned between the gongs 46 which are supported on the base plate 53by the brackets 5-1 and screws 55. A biasing s ring 49 constrains thearmature against rotative movements other than in response to currentsof a particular polarity. The magnet motor may be supported above thebase plate 53 by L shaped brackets fastened to said base plate and the Ushaped permanent magnet by screws 51.

The principle of operation of this ringer is the same as that of thetelephone register described above except that the time interval betweencurrent impulses is shorter and the armature is biased againstmovementin a particular direction. The oscillations being more rapid,the inertia of the armature in the ringer should be of lower order thanthat of the armature employed in the tele phone register. The degree ofmovement may be controlled by the adjustable screws 5 In this embodimentof the invention, it is also desirable to employ an armature whosespaced pieces are shaped similarly to the armature shown in Fig. 2 inorder that for movements in its normal operating range it will be freeof any torque due to the mag netic flux of the permanent magnet.

Referring to Figures 6, 7 and 8 still another embodiment of thisinvention is disclosed, there taking the form of a. relay of the typeadapted to produce current variations at a definite frequency in adirect current circuit. Although the assembly of the relay may differstructurally from the register and ringer described above, its principleof operation is the same.

Supported upon a plate 56, which is mounted upon a resilient base 76similar to that shown and described in U. S. Patent 1,52? A123, issuedJanuary 20, 1925 to J. F. D. Horse, is a metal block of non-magneticmaterial. Attached to this block by screws 7. is a U-shaped permanentmagnet 57 to whose polar extremities are secured lamirated pole pieces63 having restricted porons in which energizing coils 7 2 are wound. Thelaminations comprising each pole piece are maintained adjacent byfastening screws 65. Each pole piece is secured to a pole of thepermanent magnet by a screw 7 8 passing through the elon ated portionsof the outer laminations and the permanent magnet. The armature consistsof parallel magnetic pieces disposed on opposite sides of the energizingcoils and closely adjacent the lateral faces of the pole pieces so as tooverlap their restricted and non-restricted portions. A spacer member71, which may be welded or soldered or otherwise secured to each of thearmature pieces, maintains them at a desired separation. Each armaturepiece is fastened by screws 64- to-a T-shaped member 60 of spring metalwhich has a rectangular termination 73 held within a similarly shapedrecess in the forwardly extending arm 59 of the bracket 58, which ismounted upon the permanentmagnet 57 and secured thereto by screws 74:,so that the member 60 may be held tightly in the arm 59. The latter issplit at 7 5 and a screw 69 is provided passing through the bifurcationswhereby the termination 73 may be rigidly clamped in the recess. Theupper armature piece may be provided with threaded extensions 67integral therewith, or consisting of studs, upon which movable weights68 may be placed so that the natural period of the armature may beadjusted to the desired value. Extending from one armature piece is areed 61 adapted to vibrate Within the contact block 62 which may besimilar to that shown and described in U. S. Patent 1,586,549, issuedJune 1, 1926 to J. R. Fry.

By initially properly dimensioning the armature pieces 70, the spacermember 71, the reed 61, the member 60, and, after assembly, by adjustingthe positions of the Weights 68 and the degree of clamping of theterminations 73, the armature may be made to respond to a variable forceof a single frequency. The operation of this device as a relay issimilar to its operation in the other devices described, the passageof-alternating currents through the energizing coils 7 2 producingregions of greater or lesser magnetic strength in the non-restrictedportions of the lateral faces of the pole pieces 63 causing the armatureto oscillate so as to assume positions in which the reluctance ofthemagnetic circuit is at a minimum. In so oscillating at the fre quencyto which the armature has been tuned to vibrate, the reed 61 will becaused to complete and interrupt the circuit connected to.

the contact block 62. The efliciency of this relay in comparison withpreviously proposed devices of like function should be higher inasmuchas the small air gaps employed allow high flux densities to be used andrelatively large movements of the vibrating member without anypossibility of the latter freezing.

It is apparent that the magnetic device described above With referenceto metering, ringing and relaying apparatus, may have a variety of otherapplications, for instance, it might be used as a driving unit in a loudspeaking telephone. The armature could be made sufficiently low in massto respond to the voice frequencies to be reproduced and the movement ofthe armature could be communicated toa diaphragm by a reed connectedthereto. It is not intended by the recitation of such particular uses oradaptations to limit the scope of this invention other than is indicatedby the appended claims.

WVhat is claimed is:

1. The combination in a magnetic device of a field structure including asource of unidirectional magnetic fiuX having a plurality of polepieces, said pole pieces having restrictions intermediate their ends,energizing coils in said restrictions, and an armature comprising twoparallel pieces one on one side of said coils and one on the other sideof sai coils and arranged to oscillate in such manner as to overlaprestricted and unrestricted portions of said pole pieces.

2. The combination in a magnetic device of a permanent magnet, polepieces adjacent to the poles of said permanent magnet, a coil woundaround each pole piece intermediate its ends and an armature comprisinga plurality of pieces disposed parallel to and arranged to oscillate ona shaft extending perpendicupole pieces.

3. The combination in a magnetic device of a permanent magnet and polepieces therefor, said pole pieces having restrictions therein,energizing coils in said restrictions, and an armature mounted tooscillate in such a manner as to overlap the restricted and unrestrictedparts,of said electromagnetic members on either side of saidrestrictions, the sides of said armature being so shaped that When saidarmature is in its extreme position one side of the armature issubstantially parallel to the edge of the coil restriction.

4. The combination in a magnetic device of a field structure including asource of unidirectional magnetic fiuX and a plurality of pole pieces,each pole piece having a restriction therein and an energizing coil insaid restriction, an armature comprising spaced parallel pieces mountedon opposite sides of the pole pieces for oscillation relative thereto,and means driven by said armature.

5. The combination in a magnetic device of a U shaped permanent magnet,pole pieces adjacent each pole thereof, said pole pieces each having arestricted portion and an energizing coil mounted therein, an armaturecomprising two parallel pieces one on one sideof said coils and one onthe other side of said coils, said pieces mounted on a shaft extendingperpendicular to the plane of the lateral faces of said pole pieces, andmeans driven by said armature.

6. The combination in a magnetic device of a permanent magnet, polepieces adjacent thereto, each pole piece having a restriction thereinand an energizing coil in said restriction, and an armature comprisingspaced pieces mounted on opposite sides of the pole pieces foroscillation relative thereto in response to the current impulses passingthrough each coil.

7. A magnetic device comprising a field structure including a source ofunidirectional magnetic flux and a plurality of pole pieces, each polepiece having a restriction therein, an energizing coil in eachrestriction, and an armature supported parallel to the restricted andunrestricted portions of at least one lateral face of each of saidpolepieces and adapted to oscillate in a plane parallel thereto in responseto current impulses traversing said energizing coils.

8. A magnetic device comprising a permanent magnet, pole pieces, eachpole piece having a restriction therein in which an energizing coil iswound, and an armature supported adjacent the lateral faces of said polepieces, the width of said armature and that of the coil restrictionbeing so proportioned that for movements of the armature in its normaloperating range it will be substantially free of any torque due to themain polarizing flux.

9. A magnetic device comprising a U shaped source of unidirectionalmagnetic flux, pole pieces adjacent the extremities thereof, a member ofnon-magnetic material between said extremities, said member beingsecured to said pole pieces and having for- Wardly extending portions,and an armature m disposed adjacent the lateral faces of said polepieces, said armature being pivotally supported between the extendingportions of said non-magnetic member.

In Witness whereof, I hereunto subscribe my name this 21st day of arch,1930.

EDWARD J. PRATT.

